Test sensors are often used in assays for determining the concentration of an analyte in a liquid sample. A liquid sample is deposited in a reaction area of the test sensor that includes a reagent. The sample and the reagent mix produce a measurable reaction indicating the concentration of the analyte in the liquid sample. The reaction is measured with a test device that receives the test sensor.
Testing for the concentration of glucose in blood is a common use for test sensors. Those who have irregular blood-glucose concentration levels are often medically required to self-monitor their blood-glucose concentration level. Utilizing a testing device that implements a test sensor is one means that people use to monitor their blood-glucose concentration levels. Test sensors are also used for determining the concentration of or determining the presence of various other analytes (e.g., fructosamine, hemoglobin, cholesterol, glucose, alcohol, drugs, etc.) in a variety of body fluids (e.g., blood, interstitial fluid, saliva, urine, etc.). Test sensors including appropriate reagents can be used in the harvesting of most any liquid sample for the determination of the concentration of an analyte in that sample.
The type of reagent implemented in the test sensor depends on the type of measuring used. For example, in a colorimeteric assay, the color change of a reaction area containing a reagent following contact with the sample is measured to determine the concentration of the analyte of interest in the sample. The degree of color change is measured using an optical sensor(s) that converts the degree of color change to electrical signals that are evaluated with diagnostic equipment. For example, the optical device may measure the amount of light reflected from, or transmitted through, the reaction area. In other embodiments of the present invention, the amount of infrared light absorbed by the reaction of the analyte in the sample and the reagent is measured. Colorimetric testing is described in detail in U.S. Pat. No. 5,723,284 entitled “Control Solution and Method for Testing the Performance of an Electrochemical Device for Determining the Concentration of an Analyte in Blood,” which is incorporated herein by reference in its entirety. Colorimetric testing is also described in detail in U.S. Pat. Nos. 6,181,417 B1 (entitled “Photometric Readhead with Light Shaping Plate”), 5,518,689 (entitled “Diffuse Light Reflectance Readhead”), and 5,611,999 (entitled “Diffuse Light Reflectance Readhead”), each of which is incorporated herein by reference in its entirety.
The reagent that is used in the test sensor is a chemical agent that is costly to produce. Thus, it is desirable to limit the amount of reagent used and to reduce any waste of the reagent. Current manufacturing processes waste the costly reagent by impregnating more test membrane material than necessary. The test sensors include a membrane that is impregnated with the reagent during manufacturing by dipping, which entails submerging a test membrane sheet in the reagent. Test sensor disks (i.e., cut sections sized for inclusion in a test sensor) are cut from the impregnated membrane sheet which results in wasted portions of the reagent impregnated sheet. Further, picking and placing the reagent impregnated sensor disks into the test sensor introduces material handling issues due to the sensitivity of the reagent which impacts the complexity and cost of the test sensor manufacturing process.